1. Field of the Invention
The present invention relates to integrated electronic elements with variable electrical characteristics, especially for microwave frequencies.
Various microwave components have been created over the past few decades: diodes, then microwave transistors, notably made of GaAs, and then monolithic microwave integrated circuits (MMICs).
2. Description of the Prior Art
However, the technologies of miniaturization have not yet properly resolved the problems of the manufacture of certain integrated circuit components that could be used in large numbers and at low cost on very small surfaces, especially in electronic scanning antennas such as those used in "antifading" communications devices, communications with moving bodies (whether civilian or military) and in civilian radars (radars for landing systems, anticollision radars etc.). The components used in the phase-shifting circuits of these antennas may include ferrite circuits which are far too bulky or PIN diodes which show high losses and a high level of static power consumption. Certain active antennas use GaAs integrated circuits that are far too costly for many civilian applications and for mass production.
An object of the present invention relates to integrated electronic elements with variable electrical characteristics, especially for microwave frequencies, these characteristics being easily controllable without any need for bulky control elements while at the same time consuming a negligible amount of electrical power, these elements having negligible losses and working efficiently in a wide range of frequencies while being practically insensitive to radiation, easy and inexpensive to manufacture and compatible with the integration of microwave microstrip lines, especially on silicon-based insulator substrates, and being compatible with industrial techniques for the manufacture of digital circuits (especially CMOS circuits). The variable electrical characteristics are, in particular: the capacitance, the impedance, the length of the electrical path length, or the layout of this path length.